The present invention relates to a resonating apparatus in a dielectric substrate; and, more particularly, to a dielectric substrate resonator, which has a three-dimensional structure for coupling with a microstrip line, for obtaining high Q by reducing dielectric loss and conductivity loss.
Recently, there is an increasing demand for communication systems using microwaves in the mobile and satellite communication fields. It is also a trend in the information communication field that devices are downsized and the communication frequency band moved to a higher frequency band. In personal mobile communication systems such as PCS, satellite communication, or satellite broadcasting, a GHz frequency band is used for communication.
An important component of equipment using the high frequency band is the microwave dielectric device, which has been widely developed to be used as a dielectric resonating filter. By microwave is meant frequencies ranging from 300 MHz to 300 GHz.
FIG. 1 illustrates a structure for coupling a microstrip line 12 with a dielectric resonator 14 adhered to a substrate. A dielectric resonator in accordance with the prior art, as shown in FIG. 1, is generally used in multi-layer circuits such as monolithic microwave integrated circuits (MMICs) due to its simple structure.
The dielectric resonator 14 in accordance with the prior art is adhered to an upper side of a dielectric substrate 10, which is made of GaAs. The microstrip line 12, which is separated horizontally from the dielectric resonator 14, is arranged on the upper side of the dielectric substrate 10. When the length of the microstrip line 12 is xc2xd xcex, where xcex is the wavelength of the microwave, and when the microstrip line 12 and the dielectric substrate 10 are composed of gold and GaAs respectively, the Q of the microstrip line 12 is calculated by Equation (1).                               Q          u                =                              β                          2              ⁢                              (                                                      α                    c                                    +                                      α                    d                                                  )                                              =          66.8                                    Equation        ⁢                  xe2x80x83                ⁢                  (          1          )                    
where xcex2 is a propagation constant, xcex1c is an attenuation due to conductivity loss and xcex1d is the attenuation due to dielectric loss.
xcex1c and xcex1d in Equation (1) are calculated by Equations (2) and (3), respectively.                               α          c                =                              R            s                                              Z              0                        ⁢            W                                              Equation        ⁢                  xe2x80x83                ⁢                  (          2          )                    
where Rs, Z0 and W are a surface resistance, a characterization impedance and a width of the microstrip line 12, respectively.                               α          d                =                                            k              0                        ⁢                                          ϵ                r                            ⁡                              (                                                      ϵ                    e                                    -                  1                                )                                      ⁢            tan            ⁢                          xe2x80x83                        ⁢            δ                                2            ⁢                                          ϵ                e                                      ⁢                          (                                                ϵ                  r                                -                1                            )                                                          Equation        ⁢                  xe2x80x83                ⁢                  (          3          )                    
where xcex5r is a relative dielectric permittivity, xcex5e is an effective dielectric permittivity and tanxcex4 is a loss tangent of the dielectric substrate.
Referring to Equations (1) to (3) , when Z0 is 50xcexa9, tanxcex4 is 0.0006 and the resonant frequency is 10 GHz. The Q of the microstrip line is about 66.
According to Equation (1), the Q of the dielectric resonator 14 depends on two factors, xcex1c and xcex1d, wherein xcex1c is inversely proportional to Z0 and W. When the dielectric resonator 14 of the prior art is applied to a multiplayer circuit, a fluid dielectric substance is used to configure a microstrip line. In general, the height of the fluid dielectric substance, e.g., BCB, is limited to 40 xcexcm. The smaller the height of the fluid dielectric substance, the narrower the width of the microstrip line. Therefore, Q becomes smaller.
Further, the conductivity loss of the microstrip line 12 affects the energy loss of the dielectric resonator 14. Accordingly, the dielectric resonating device in accordance with the prior art is not suitable for obtaining the high Q required in microwave applications.
It is therefore an object of the present invention to provide a resonating apparatus that is suitable for use in microwave including multi-layer circuits such as MMICs that require high integrity and high Q.
In accordance with the present invention, there is provided a resonating apparatus comprising: a dielectric supporting substrate; a dielectric resonator which is formed on the dielectric supporting substrate; a fluid dielectric membrane which overspreads the dielectric resonator; and a microstrip line which is arranged in the fluid substrate membrane so that it is coupled with the dielectric resonator.